In recent years, people have developed various light weight and small size flat panel display devices for replacing cathode ray tube. Examples of such flat panel display devices include a liquid crystal display panel, a plasma display panel and an electroluminescent display panel. The electroluminescent display panel realizes the normal display of the display panel through an electroluminescent device within the display panel. According to different materials of a light-emitting layer, electroluminescent devices are divided into two categories: inorganic light-emitting and organic light-emitting. The organic light-emitting device is referred to as a new generation of display technology, since the organic light-emitting device has a high response speed, a high luminous efficiency, a strong luminance, and a wide viewing angle.
A light-emitting device within the organic light-emitting display panel is a current driving light-emitting device whose light emission luminance is determined by a driving current of a driving transistor. There are large differences among various drive transistors due to factors such as working conditions, production process and the like, therefore, there exists a phenomenon of uneven screen among different pixels on the display panel due to a threshold voltage drift of the driving transistor. At present, in the existing art, the threshold voltage of the driving transistor is compensated generally by means of external compensation and internal compensation so as to eliminate the problem of uneven display caused by the threshold voltage drift. According to the external compensation, the threshold voltage of the driving transistor is acquired by an integrated process unit (other than the pixel driving circuit itself) of the organic light-emitting display panel, and then a data voltage is compensated based on the acquired threshold voltage. According to the internal compensation, the acquisition and compensation of the threshold voltage of the driving transistor is completed by the pixel driving circuit itself.
In practical applications, organic light-emitting display devices are often in an environment whose brightness is continually varying, it is urgent to adjust a display mode according to the brightness of the environment where the organic light-emitting display devices are located so as to compensate the luminance. Although both of the external compensation and the internal compensation can effectively overcome the problem of uneven screen generated due to the threshold voltage shift of the driving transistor, the luminance cannot be effectively compensated according to the environment brightness so as to improve an over bright or over dark visual experience appearing when being observed by human eyes.